Age-related changes of fibroblast density in the human periodontal ligament

Comparison of the efficiency of initial dental alignment with Invisalign® aligners changed every 7 or 14 days in mature adults: Randomized clinical trial

OBJECTIVE

To compare the anterior crowding correction after sequential use of the first 5 aligners between two aligner exchange protocols (7 and 14 days) in mature adult patients.

MATERIALS AND METHODS

Thirty-six patients over 35 years who received orthodontic treatment with Invisalign® were randomly allocated to two different aligner replacement sequence protocols: Group 1: exchange every 7 days (n = 18); and Group 2: exchange every 14 days (n = 18). All patients were scanned with iTero Element 5D® (Align Technology) in two treatment times: at pre-treatment (T1) and after using the first five aligners (T2). Little's Irregularity Index (LII) and arch widths were evaluated with OrthoCAD software. Intra and intergroup comparisons were performed with the dependent and independent t-tests. The results were considered significant for P < .05.

RESULTS

Thirty-five patients completed the study. Both groups' maxillary and mandibular Irregularity Indexesi were significantly lower at T2. There was no significant difference in inter-canine, inter-premolar, and intermolar distances. G2 (14 days) presented a greater decrease in mandibular irregularity than G1 (7 days).

CONCLUSION

Both exchange protocols (7 and 14 days) effectively correct anterior crowding in the initial phase of orthodontic treatment with aligners in mature adult patients. However, the 14-day exchange protocol provided a greater correction in mandibular anterior crowding in the evaluated period than the 7-day exchange protocol.

Radiological assessment of periodontal ligament space visibility on third molars for forensic age assessment - a comparison study of three different staging scales

Various staging scales have been proposed for the assessment of the visibility of the periodontal ligament space of mandibular third molars on dental panoramic radiographs (PANs) for forensic age assessment in living individuals. However, up to now, there has been no systematic comparison between these staging scales available. We directly compared the 2010 staging scale proposed by Olze et al. with the 2017 staging by Lucas et al. and the 2020 staging by Guo et al. in a German study population. We evaluated 233 PANs from 115 females and 118 males aged 20.0 to 40.9 years using three independent examiners, with one examiner conducting two assessments. We examined the correlation between age and stage, as well as the inter- and intra-rater reliabilities. While the point estimates for the correlation coefficient and the reliability measures were lowest for the Guo scale and highest for the Olze scale, confidence intervals showed a large overlap, particularly for the scales of Olze et al. and Lucas et al. The correlation coefficients between stage and age were consistently lower in females than in males across all methods. In summary, we showed that the staging scales of Olze et al. and Lucas et al. were very similar. The Olze method showed higher point estimates across all analyses, and because there are more reference data available for this method, we argue that it should be preferred as the method of choice for further studies in the field. However, Guo method could be considered for instances, in which the inter-radicular periodontal ligament is not evaluable.

A Mouse Model for Studying the Development of Apical Periodontitis with Age

Older age is associated with reduced immune function. Our aim was to study how age affects the development of apical periodontitis (AP). AP was induced in two age groups of mice (young vs. adult). Histological samples were stained by Hematoxylin Eosin, Brown and Brenn, and Tartrate-Resistant Acid Phosphatase. In addition, the samples were scanned by Micro-Computerized-Tomography (micro-CT) to evaluate apical constriction and periapical lesion size. Cell density in the periapical region was computationally assessed. Moreover, lesion immune cell populations were characterized by flow cytometry and immunofluorescence. The young group presented more canals with necrotic radicular pulp compared to the adults. There was no difference in bacteria location in the canals between the groups. Apical constriction size was larger in the young mice compared to the adults. The periapical cell density was higher in the young group, while the dominant immune cells in the lesions were neutrophils, which also exhibited the highest young/adult ratio. Immunofluorescence demonstrated neutrophils in the lesion. More osteoclasts were present in the lesions of the young mice, in correlation to the higher volume of bone resorption in this group. Overall, we conclude that the immune reaction to AP stimuli was attenuated in the adult mice compared to the young.

Epigenetic alterations in aging tooth and the reprogramming potential

Tooth compartments and associated supportive tissues exhibit significant alterations during aging, leading to their impaired functioning. Aging not only affects the structure and function of dental tissue but also reduces its capacity to maintain physiological homeostasis and the healing process. Decreased cementocyte viability; diminished regenerative potential of stem cells residing in the pulp, alveolar bone and periodontal ligament; and impaired osteogenic and odontogenic differentiation capacity of progenitor cells are among the cellular impacts associated with oral aging. Various physiological and pathological phenomena are regulated by the epigenome, and hence, changes in epigenetic markers due to external stimuli have been reported in aging oral tissues and are considered a possible molecular mechanism underlying dental aging. The role of nutri-epigenetics in aging has emerged as an attractive research area. Thus far, various nutrients and bioactive compounds have been identified to have a modulatory effect on the epigenetic machinery, showing a promising response in dental aging. The human microbiota is another key player in aging and can be a target for anti-aging interventions in dental tissue. Considering the reversible characteristics of epigenetic markers and the potential for environmental factors to manipulate the epigenome, to minimize the deteriorative effects of aging, it is important to evaluate the linkage between external stimuli and their effects in terms of age-related epigenetic modifications.

Cellular ageing of oral fibroblasts differentially modulates extracellular matrix organization

BACKGROUND AND OBJECTIVES

Ageing is associated with an impaired cellular function that can affect tissue architecture and wound healing in gingival and periodontal tissues. However, the impact of oral fibroblast ageing on the structural organization of the extracellular matrix (ECM) proteins is poorly understood. Hence, in this study, we investigated the impact of cellular ageing of oral fibroblasts on the production and structural organization of collagen and other ECM proteins.

METHODS

Oral fibroblasts were serially subcultured, and replicative cellular senescence was assessed using population doubling time, Ki67 counts and expression of P21^WAFI . The production and structural organization of ECM proteins were assessed at early (young-oFB) and late (aged-oFB) passages. The thickness and pattern of collagen produced by live cultures of young- and aged-oFB were assessed using a label-free and non-invasive second harmonic generation (SHG)-based multiphoton imaging. Expression of other ECM proteins (fibronectin, fibrillin, collagen-IV and laminins) was evaluated using immunocytochemistry and confocal microscopy-based depth profile analysis.

RESULTS

Aged-oFB displayed a higher population doubling time, lower Ki67+ cells and higher expression of P21^WAFI indicative of slower proliferation rate and senescence phenotype. SHG imaging demonstrated that young-oFB produced a thick, interwoven network of collagen fibres, while the aged-oFB produced thin and linearly organized collagen fibres. Similarly, analysis of immunostained cultures showed that young-oFB produced a rich, interwoven mesh of fibronectin, fibrillin and collagen-IV fibres. In contrast, the aged-oFB produced linearly organized fibronectin, fibrillin and collagen-IV fibres. Lastly, there was no observable difference in production and organization of laminins among the young- and aged-oFB.

CONCLUSION

Our results suggest that oral fibroblast ageing impairs ECM production and more importantly the organization of ECM fibres, which could potentially impair wound healing in the elderly.

Pulp Regeneration: Current Approaches, Challenges, and Novel Rejuvenating Strategies for an Aging Population

We showed the safety and efficacy of pulp regenerative therapy by the autologous transplantation of mobilized dental pulp stem cells with granulocyte colony-stimulating factor in a pilot clinical study of young and middle-aged pulpectomized teeth. An experimental study in dogs further demonstrated an age-dependent decline in the amount of regenerated pulp tissue. In our society, in which people will soon live beyond 100 years, this therapy should be efficacious for contributing to the functional survival and endurance of the tooth not only for pulpectomized young teeth but also for aged teeth with periapical disease. However, there are 2 challenges: 1 is enhancing pulp regeneration in aged teeth, and another is complete disinfection before cell transplantation. Thus, this review presents trypsin pretreatment for the former and a novel irrigant, nanobubbles with antibacterial nanopolymers, for the latter, thus demonstrating potential utility for pulp regenerative therapy in aged teeth with periapical disease.

Treatment of Pulpectomized Teeth With Trypsin Prior to Transplantation of Mobilized Dental Pulp Stem Cells Enhances Pulp Regeneration in Aged Dogs

There is an age-dependent decline of pulp regeneration, due to the decline of migration, proliferation, and cell survival of resident stem cells. Trypsin is a proteolytic enzyme clinically used for tissue repair. Here, we investigated the effects of trypsin pretreatment of pulpectomized teeth prior to cell transplantation on pulp regeneration in aged dogs. The amount of regenerated pulp was significantly higher in trypsin-pretreated teeth compared to untreated teeth. Trypsin pretreatment increased the number of cells attached to the dentinal wall that differentiated into odontoblast-like cells. The trypsin receptor, PAR2, was higher in vitro expression in the periodontal ligament cells (PDLCs) from aged dogs compared to those from young. The direct effects of trypsin on aged PDLCs were increased expression of genes related to immunomodulation, cell survival, and extracellular matrix degradation. To examine the indirect effects on microenvironment, highly extracted proteins from aged cementum were identified by proteomic analyses. Western blotting demonstrated that significantly increased fibronectin was released by the trypsin treatment of aged cementum compared to young cementum. The aged cementum extract (CE) and dentin extract (DE) by trypsin treatment increased angiogenesis, neurite extension and migration activities as elicited by fibronectin. Furthermore, the DE significantly increased the mRNA expression of immunomodulatory factors and pulp markers in the aged DPSCs. These results demonstrated the effects of trypsin on the microenvironment in addition to the resident cells including PDLCs in the aged teeth. In conclusion, the potential utility of trypsin pretreatment to stimulate pulp regeneration in aged teeth and the underlying mechanisms were demonstrated.

Age effect on orthodontic tooth movement rate and the composition of gingival crevicular fluid : A literature review

PURPOSE

To evaluate and form a comprehensive understanding of the effect of patient age on bone remodeling and consequently on the rate of orthodontic tooth movement (OTM).

METHODS

A systematic search in PubMed and Embase from 1990 to December 2017 was performed and completed by a hand search. Prospective clinical trials which investigated the rate of OTM and/or studies assessing age-related changes in the composition of gingival crevicular fluid (GCF) in older compared to younger study groups were included. Study selection, data extraction and risk of bias were assessed by two authors.

RESULTS

Eight studies fulfilled the inclusion criteria. Among them, four evaluated the rate of OTM and six investigated mediators in the GCF (prostaglandin E₂, interleukin [IL]-1β, IL‑6, IL‑1 receptor antagonist, receptor activator of nuclear factor kappa‑Β ligand, osteoprotegerin, granulocyte-macrophage colony-stimulating factor, pentraxin 3). Patient age ranged between 16 and 43 years for older and <16 years for younger groups. In most of the studies, the younger patients showed faster OTM in the first phase of treatment and more pronounced cytokine levels. Older patients had a delayed reaction to orthodontic forces.

CONCLUSION

The small number of included studies and large heterogeneity in study design give limited clinical evidence that the older patients are less responsive to orthodontic force in comparison to younger patients. The initial cellular response to orthodontic force is expected to be delayed in older patients. Control intervals during orthodontic treatment should be adjusted to the individual's treatment response.

Mechanoadaptive Responses in the Periodontium Are Coordinated by Wnt

Despite an extensive literature documenting the adaptive changes of bones and ligaments to mechanical forces, our understanding of how tissues actually mount a coordinated response to physical loading is astonishingly inadequate. Here, using finite element (FE) modeling and an in vivo murine model, we demonstrate the stress distributions within the periodontal ligament (PDL) caused by occlusal hyperloading. In direct response, a spatially restricted pattern of apoptosis is triggered in the stressed PDL, the temporal peak of which is coordinated with a spatially restricted burst in PDL cell proliferation. This culminates in increased collagen deposition and a thicker, stiffer PDL that is adapted to its new hyperloading status. Meanwhile, in the adjacent alveolar bone, hyperloading activates bone resorption, the peak of which is followed by a bone formation phase, leading ultimately to an accelerated rate of mineral apposition and an increase in alveolar bone density. All of these adaptive responses are orchestrated by a population of Wnt-responsive stem/progenitor cells residing in the PDL and bone, whose death and revival are ultimately responsible for directly giving rise to new PDL fibers and new bone.

Osteoporotic Changes in the Periodontium Impair Alveolar Bone Healing

Osteoporosis is associated with decreased bone density and increased bone fragility, but how this disease affects alveolar bone healing is not clear. The objective of this study was to determine the extent to which osteoporosis affects the jaw skeleton and then to evaluate possible mechanisms whereby an osteoporotic phenotype might affect the rate of alveolar bone healing following tooth extraction. Using an ovariectomized mouse model coupled with micro-computed tomographic imaging, histologic, molecular, and cellular assays, we first demonstrated that the appendicular and jaw skeletons both develop osteoporotic phenotypes. Next, we demonstrated that osteoporotic mice exhibit atrophy of the periodontal ligament (PDL) and that this atrophy was accompanied by a reduction in the pool of osteoprogenitor cells in the PDL. The paucity of PDL-derived osteoprogenitor cells in osteoporotic mice was associated with significantly slower extraction socket healing. Collectively, these analyses demonstrate that the jaw skeleton is susceptible to the untoward effects of osteoporosis that manifest as thinner, more porous alveolar bone, PDL thinning, and slower bone repair. These findings have potential clinical significance for older osteopenic patients undergoing reconstructive procedures.

Salivary Thiocyanate, Uric Acid and pH as Biomarkers of Periodontal Disease in Tobacco Users and Non-Users- An In-Vitro Study

INTRODUCTION

Biomarkers of tobacco exposure are used to confirm the absorption of specific smoke constituents in a quantitative manner.

MATERIALS AND METHODS

Periodontal status was measured by Community periodontal Index (WHO). Salivary thiocyanate was determined using spectrophotometric analysis, Salivary uric acid concentration was determined using the enzymatic uric acid assay reagent. pH was measured using pH strips.

RESULTS

Proportion of participants with periodontal pockets of 4-5mm was highest among tobacco smokers (80.0%) and periodontal pockets of 6mm or more were observed to be higher among tobacco chewers (26.67%). When LOA scores among tobacco chewers were recorded 26.7% of them presented with attachment loss of 0-3mm. 46.7% of them were affected with loss of attachment of 4-5mm and loss of attachment 6-8mm was found in 16.7%. 6.7% of them were found to be having loss of attachment of 9-11mm. 3.3% of them were found to be having loss of attachment of 12mm or more. The LOA scores in non- tobacco users showed 46.7% of 0-3mm, 50.0% of 4-5mm and 3.33% of 6-8mm attachment loss. The mean level of thiocyanate level detected in saliva of tobacco smokers was 172 ± 54.7 μg/ml and 203.70± 45.7 μg/ml in tobacco chewers. The mean uric acid levels was found to be 2.54 ±0.63 (μg/dl) in smokers and 2.65 ± 0.37(μg/dl) in chewers and in non tobacco users it was 2.33 ± 0.47 μg/dl.

CONCLUSION

Tobacco users had significantly higher concentration of SCN levels than non-users.

Both 25-hydroxyvitamin-D3 and 1,25-dihydroxyvitamin-D3 reduces inflammatory response in human periodontal ligament cells

Periodontitis is an inflammatory disease leading to the destruction of periodontal tissue. Vitamin D3 is an important hormone involved in the preservation of serum calcium and phosphate levels, regulation of bone metabolism and inflammatory response. Recent studies suggest that vitamin D3 metabolism might play a role in the progression of periodontitis. The aim of the present study was to examine the effects of 25(OH)D3, which is stable form of vitamin D3 in blood, and biologically active form 1,25(OH)2D3 on the production of interleukin-6 (IL-6), interleukin-8 (IL-8), and monocyte chemotactic protein-1 (MCP-1) by cells of periodontal ligament. Commercially available human periodontal ligament fibroblasts (hPdLF) and primary human periodontal ligament cells (hPdLC) were used. Cells were stimulated with either Porphyromonas gingivalis lipopolysaccharide (LPS) or heat-killed P. ginigvalis in the presence or in the absence of 25(OH)D3 or 1,25(OH)2D3 at concentrations of 10-100 nM. Stimulation of cells with either P. gingivalis LPS or heat-killed P. gingivalis resulted in a significant increase of the expression levels of IL-6, IL-8, and MCP-1 in gene as well as in protein levels, measured by qPCR and ELISA, respectively. The production of these pro-inflammatory mediators in hPdLF was significantly inhibited by both 25(OH)D3 and 1,25(OH)2D3 in a dose-dependent manner. In primary hPdLCs, both 25(OH)D3 and 1,25(OH)2D3 inhibited the production of IL-8 and MCP-1 but have no significant effect on the IL-6 production. The effect of both 25(OH)D3 and 1,25(OH)2D3 was abolished by specific knockdown of vitamin D3 receptor by siRNA. Our data suggest that vitamin D3 might play an important role in the modulation of periodontal inflammation via regulation of cytokine production by cells of periodontal ligament. Further studies are required for better understanding of the extents of this anti-inflammatory effect and its involvement in the progression of periodontal disease.